Capacitor and method for fabricating the same

ABSTRACT

A capacitor includes a lower electrode, a dielectric structure over the lower electrode, the dielectric structure including at least one crystallized zirconium oxide (ZrO 2 ) layer and at least one amorphous aluminum oxide (Al 2 O 3 ) layer, and an upper electrode formed over the dielectric structure. A method for fabricating a capacitor includes forming a lower electrode over a certain structure, forming a dielectric structure including at least one crystallized zirconium oxide (ZrO 2 ) layer and at least one amorphous aluminum oxide (Al 2 O 3 ) layer over the lower electrode, and forming an upper electrode over the dielectric structure.

The present patent application is a Divisional of application Ser. No.11/595,548, filed Nov. 10, 2006 now U.S. Pat. No. 7,616,426.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims priority of Korean patent applicationnumber(s) 10-2005-0107399, filed on Nov. 10, 2005 which is incorporatedby reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor device and a method forfabricating the same, and more particularly, to a capacitor with adielectric structure advantageous of reducing leakage current, and amethod for fabricating the same.

As dielectric structures of capacitors for sub-60 nm dynamic randomaccess memories (DRAMs), many researchers have attempted to form a thinlayer of zirconium oxide (ZrO₂) using an atomic layer deposition (ALD)method. However, when an ALD method is used to form a thin layer ofZrO₂, ZrO₂ is usually crystallized at a low temperature of 300° C.Hence, if a single layer of ZrO₂ is used as a dielectric structure,current is likely to leak.

For this reason, a laminate structure including a ZrO layer and analuminum oxide (Al₂O₃) layer, which has high crystallizationtemperature, or an alloy including ZrO₂ and Al₂O₃ is applied to reducethe crystallization.

FIG. 1 illustrates a cross-sectional view of a conventional capacitorstructure. The capacitor includes a tower electrode 11, a dielectricstructure 12, and an upper electrode 13 formed in sequential order. Thedielectric structure 12 includes amorphous thin ZrO₂ layer 12A and anamorphous thin Al₂O₃ layer 12B.

However, since the thin ZrO₂ layer and the thin Al₂O₃ layer are atamorphous phase, relative dielectric constants thereof are usuallysmall. Thus, the thicknesses of the ZrO₂ layer and the Al₂O₃ layer needto be reduced to obtain a desired level of capacitance. In such a case,leakage current is likely to occur, and thus, the implementation of theaforementioned dielectric structure may become limited in actualpractice.

SUMMARY OF THE INVENTION

Various embodiments of the present invention are directed to provide acapacitor suitable for a certain level of capacitance by improving adielectric constant and a leakage current characteristic, and a methodfor fabricating the same.

In accordance with an aspect of the present invention, there is provideda capacitor, including a lower electrode, a dielectric structure overthe lower electrode, the dielectric structure including at least onecrystallized zirconium oxide (ZrO₂) layer and at least one amorphousaluminum oxide (Al₂O₃) layer, and an upper electrode formed over thedielectric structure.

In accordance with another aspect of the present invention, there isprovided a capacitor, including a lower electrode, a dielectricstructure formed over the lower electrode, the dielectric structureincluding at least one crystallized zirconium oxide (ZrO₂) layer and atleast one amorphous zirconium aluminum oxide ZrAlO_(x)) layer, where ‘x’representing an atomic ratio of oxygen is a positive number, and anupper electrode.

In accordance with another aspect of the present invention, there isprovided a method for fabricating a capacitor, the method includingforming a lower electrode over a certain structure, forming a dielectricstructure including at least one crystallized zirconium oxide (ZrO₂)layer and at least one amorphous aluminum oxide (Al₂O₃) layer over thelower electrode, and forming an upper electrode over the dielectricstructure.

In accordance with a further another aspect of the present invention,there is provided a method for fabricating a capacitor, the methodincluding forming a lower electrode over a certain structure, forming adielectric structure including at least one crystallized zirconium oxide(ZrO₂) layer and at least one amorphous zirconium aluminum oxide(ZrAlO_(x)) layer, where ‘x’ representing an atomic ratio of oxygen is apositive number, over the lower electrode, and forming an upperelectrode over the dielectric structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of a conventional capacitorstructure.

FIG. 2A illustrates a graph of surface roughness associated with thethickness of a zirconium oxide (ZrO₂) layer in accordance with anembodiment of the present invention.

FIG. 2B illustrates transmission electron microscopic (TEM) images of aZrO₂ layer with different levels of surface roughness at differentphases in accordance with an embodiment of the present invention.

FIG. 3 illustrates a graph of a degree of crystallization associatedwith the thicknesses of ZrO₂ and aluminum oxide (Al₂O₃) layers inaccordance with an embodiment of the present invention.

FIG. 4A illustrates a cross-sectional view of a capacitor structure in asemiconductor device in accordance with a first specific embodiment ofthe present invention.

FIG. 4B illustrates a simplified diagram of a capacitor structure inaccordance with the first specific embodiment of the present invention.

FIG. 5 illustrates a simplified diagram of a capacitor structure inaccordance with a second specific embodiment of the present invention.

FIG. 6 illustrates a simplified diagram of a capacitor structure inaccordance with a third specific embodiment of the present invention.

FIG. 7 illustrates a simplified diagram of a capacitor structure inaccordance with a fourth specific embodiment of the present invention.

FIG. 8 illustrates a simplified diagram of a capacitor structure inaccordance with a fifth specific embodiment of the present invention.

FIG. 9 illustrates a simplified diagram of a capacitor structure inaccordance with a sixth specific embodiment of the present invention.

FIG. 10 illustrates a simplified diagram of a capacitor structure inaccordance with a seventh specific embodiment of the present invention.

FIG. 11 illustrates a simplified diagram of a capacitor structure inaccordance with an eighth specific embodiment of the present invention.

FIG. 12 is a simplified diagram to illustrate an atomic layer deposition(ALD) method implemented for providing the capacitor structures inaccordance with the first to eighth specific embodiments of the presentinvention.

FIG. 13 illustrates a simplified diagram of a capacitor structure inaccordance with a ninth specific embodiment of the present invention.

FIG. 14 illustrates a simplified diagram of a capacitor structure inaccordance with a tenth specific embodiment of the present invention.

FIG. 15 is a simplified diagram to illustrate an ALD method implementedfor providing the capacitor structures in accordance with the ninth totenth specific embodiments of the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

FIG. 2A illustrates a graph of surface roughness associated with thethickness of a zirconium oxide (ZrO₂) layer in accordance with anembodiment of the present invention. FIG. 2B illustrates transmissionelectron microscopic (TEM) images of a ZrO₂ layer with different levelsof surface roughness at different phases in accordance with anembodiment of the present invention. Referring to FIG. 2A, the ZrO₂layer is formed at approximately 300° C. using an atomic layerdeposition (ALD) method, and the surface roughness of the ZrO₂ layer atdifferent thicknesses is measured in the unit of root-mean-square (RMS).As the thickness of the ZrO₂ layer increases, the surface roughnessthereof increases as well.

In more detail, when the ZrO₂ layer is approximately 45 Å thick, thesurface roughness increases abruptly. This behavior is caused by thecrystallization of ZrO₂, and the TEM images illustrated in FIG. 2Bverify the ZrO₂ crystallization.

In the graph illustrated in FIG. 2A, reference label ‘A’ denotes theZrO₂ layer at amorphous phase, while reference label ‘B’ denotes theZrO₂ layer at crystalline phase. In particular, the graph illustrated inFIG. 2A and the TEM image illustrated in FIG. 2B (see ‘C’) show that theamorphous phase of the ZrO₂ layer (see ‘A’ in FIG. 2A) is observed atapproximately 45 Å or less, and at this time, the ZrO₂ layer has a lowdielectric constant. Also, when the thickness of the ZrO₂ layer is aboveapproximately 45 Å, the ZrO₂ layer is crystallized (see ‘B’ in FIG. 2A)and has a high dielectric constant. The TEM image ‘D’ illustrated inFIG. 2B shows the ZrO₂ layer at crystalline phase.

However, although the ZrO₂ layer at amorphous phase has a low dielectricconstant, this ZrO₂ layer can reduce leakage current since the ZrO₂layer at amorphous phase does not have poor crystalline boundaries. Onthe other hand, although the ZrO₂ layer at crystalline phase has a highdielectric constant, this ZrO₂ layer is crystallized, often resulting inleakage current due to crystalline boundaries.

In the case of Al₂O₃, this crystallization does not occur till thetemperature reaches approximately 900° C. since Al₂O₃ is usuallycrystallized at high temperature. Also, Al₂O₃ is generally notcrystallized when the thickness of an Al₂O₃ layer ranges fromapproximately 200 Å to 300 Å, or above this thickness range. Theappropriate application of such distinctive characteristics of ZrO₂ andAl₂O₃ at different phases allows formation of a dielectric structurewith a high dielectric constant and low leakage current.

FIG. 3 illustrates a graph of a degree of crystallization associatedwith the thicknesses of ZrO₂ and Al₂O₃ layers in accordance with anembodiment of the present invention. In the graph, a ‘X’ region denotesthe case where the ZrO₂ and Al₂O₃ layers are at amorphous phase. A ‘Y’region denotes the case where the ZrO layer is at crystalline phasewhile the Al₂O₃ layer is at amorphous phase. A ‘Z’ region denotes thecase where the ZrO₂ and Al₂O₃ layers are at crystalline phase.

Since the ZrO₂ and Al₂O₃ layers are at amorphous phase and haverespective dielectric constants given at amorphous phase, leakagecurrent is not likely to occur due to the absence of poor crystallineboundaries despite of given low dielectric constants. In the ‘Y’ region,as mentioned above, the ZrO₂ layer is at crystalline phase, while theAl₂O₃ layer is at amorphous phase. Thus, when the ZrO₂ layer and theAl₂O₃ layer are laminated over each other, the ZrO₂ layer has a highdielectric constant, thereby allowing the dielectric constant of thedielectric structure to increase. Also, since the Al₂O₃ layer in the ‘Y’region is still at amorphous phase, the Al₂O₃ layer can block thecrystalline boundaries of the ZrO₂ layer. As a result, the leakagecurrent can be reduced.

In the ‘Z’ region, since the ZrO₂ layer and the Al₂O₃ layer arecrystallized, the dielectric constant of the dielectric structure ishigh. However, those crystalline boundaries prone to the leakage currentare not blocked by the ZrO₂ layer or the Al₂O₃ layer, and thus, theleakage current is likely to increase. Accordingly, according to theembodiments of the present invention, the ZrO₂ layer at crystallinephase and the Al₂O₃ layer at amorphous phase discovered in the ‘Y’region (i.e., high dielectric constant and low leakage current) areformed in a structure of dual, triple, multiple, or mixture layers to beused as the dielectric structure of the capacitor.

FIG. 4A illustrates a cross-sectional view of a capacitor structure in asemiconductor device in accordance with a first specific embodiment ofthe present invention. FIG. 43 illustrates a simplified diagram of acapacitor structure in accordance with the first specific embodiment ofthe present Invention. A lower electrode 24 is formed over a bottomsubstrate structure including previously formed various elements (e.g.,a substrate 21, an insulation layer 22, and a contact plug 23). A dualstructure of a crystallized thin ZrO₂ layer 25A and an amorphous thinAl₂O₃ layer 25B laminated in this sequence order is formed as adielectric structure 25 over the lower electrode 24. The crystallizedZrO₂ layer is formed to a thickness of approximately 40 Å to 150 Å,while the amorphous Al₂O₃ layer is formed to a thickness ofapproximately 2 Å to 20 Å. An upper electrode 26 is then formed over thedielectric structure 25. This dual structure of the crystallized ZrO₂layer 25A and the amorphous Al₂O₃ layer 25B allows achieving a highdielectric constant in a range of approximately 40 due to thecrystallized thin ZrO₂ layer 25A and reducing the leakage current due tothe amorphous thin Al₂O₃ layer 25B. The high dielectric constant cancontribute to improvement in large capacitance of the capacitor.

FIG. 5 illustrates a simplified diagram of a capacitor structure inaccordance with a second specific embodiment of the present invention. Adual structure of an amorphous thin Al₂O₃ layer and a crystallized thinZrO₂ layer laminated in this sequence order is formed as a dielectricstructure over a lower electrode. The amorphous Al₂O₃ layer is formed toa thickness of approximately 2 Å to 20 Å, while the crystallized ZrO₂layer is formed to a thickness of approximately 40 Å to 150 Å. An upperelectrode is then formed over the dielectric structure. This dualstructure of the amorphous Al₂O₃ layer and the crystallized ZrO₂ layerallows achieving a high dielectric constant in a range of approximately40 due to the crystallized thin ZrO₂ layer and reducing the leakagecurrent due to the amorphous thin Al₂O₃ layer. The high dielectricconstant can contribute to improvement in large capacitance of thecapacitor.

FIG. 6 illustrates a simplified diagram of a capacitor structure inaccordance with a third specific embodiment of the present invention. Adielectric structure including repeatedly formed dual structures isformed over a lower electrode. Each dual structure includes acrystallized thin ZrO₂ layer and an amorphous thin Al₂O₃ layer laminatedin sequence order. The dual structures are repeatedly formed for acertain number of times N, where N may range from approximately 2 to 10.The crystallized ZrO₂ layer is formed to a thickness of approximately 40Å to 150 Å, while the amorphous Al₂O₃ layer is formed to a thickness ofapproximately 2 Å to 20 Å. An upper electrode is then formed over thedielectric structure. This dielectric structure including the repeatedlyformed dual structures of the crystallized ZrO₂ layer and the amorphousAl₂O₃ layer allows achieving a high dielectric constant in a range ofapproximately 40 due to the crystallized thin ZrO₂ layer and reducingthe leakage current due to the amorphous thin Al₂O₃ layer. The highdielectric constant can contribute to improvement in large capacitanceof the capacitor.

FIG. 7 illustrates a simplified diagram of a capacitor structure inaccordance with a fourth specific embodiment of the present invention. Adielectric structure including repeatedly formed dual structures isformed over a lower electrode. Each dual structure includes an amorphousthin Al₂O₃ layer and a crystallized thin ZrO₂ layer laminated insequence order. The dual structures are repeatedly formed for a certainnumber of times N, where N may range from approximately 2 to 10. Theamorphous thin Al₂O₃ layer is formed to a thickness of approximately 2 Åto 20 Å, while the crystallized thin ZrO₂ layer is formed to a thicknessof approximately 40 Å to 150 Å. This dielectric structure including therepeatedly formed dual structures of the amorphous Al₂O₃ layer and thecrystallized ZrO₂ layer allows achieving a high dielectric constant in arange of approximately 40 due to the crystallized thin ZrO₂ layer andreducing the leakage current due to the amorphous thin Al₂O₃ layer. Thehigh dielectric constant can contribute to improvement in largecapacitance of the capacitor.

FIG. 8 illustrates a simplified diagram of a capacitor structure inaccordance with a fifth specific embodiment of the present invention. Atriple structure including a crystallized thin ZrO₂ layer, an amorphousthin Al₂O₃ layer, and another crystallized thin ZrO₂ layer laminated inthis sequence order is formed as a dielectric structure over a lowerelectrode. The crystallized ZrO₂ layer is formed to a thickness ofapproximately 40 Å to 150 Å, while the amorphous Al₂O₃ layer is formedto a thickness of approximately 2 Å to 20 Å. This triple structureincluding the crystallized ZrO₂ layer, the amorphous Al₂O₃ layer, andthe other crystallized ZrO₂ allows achieving a high dielectric constantin a range of approximately 40 due to the crystallized thin grow layerand reducing the leakage current due to the amorphous thin Al₂O₃ layer.The high dielectric constant can contribute to improvement in largecapacitance of the capacitor.

FIG. 9 illustrates a simplified diagram of a capacitor structure inaccordance with a sixth specific embodiment of the present invention. Atriple structure including an amorphous thin Al₂O₃ layer, a crystallizedthin ZrO₂ layer, and another amorphous thin Al₂O₃ layer laminated inthis sequence order is formed as a dielectric structure over a lowerelectrode. The amorphous Al₂O₃ layer is formed to a thickness ofapproximately 2 Å to 20 Å, while the crystallized ZrO₂ layer is formedto a thickness of approximately 40 Å to 150 Å. This triple structureincluding the amorphous Al₂O₃ layer, the crystallized ZrO₂ layer, andthe other amorphous Al₂O₃ layer allows achieving a high dielectricconstant in a range of approximately 40 due to the crystallized thinZrO₂ layer and reducing the leakage current due to the amorphous thinAl₂O₃ layer. The high dielectric constant can contribute to improvementin large capacitance of the capacitor.

FIG. 10 illustrates a simplified diagram of a capacitor structure inaccordance with a seventh specific embodiment of the present invention.A dielectric structure including repeatedly formed triple structures isformed over a lower electrode. Each triple structure includes acrystallized thin ZrO₂ layer, an amorphous thin Al₂O₃ Layer, and anothera crystallized thin ZrO₂ layer laminated in sequence order. The triplestructures are repeatedly formed for a certain number of times N, whereN may range from approximately 2 to 10. The amorphous Al₂O₃ layer isformed to a thickness of approximately 2 Å to 20 Å, while thecrystallized ZrO₂ layer is formed to a thickness of approximately 40 Åto 150 Å. This dielectric structure including the repeatedly formedtriple structures including the crystallized ZrO₂ layer, the amorphousAl₂O₃ layer, and the other crystallized ZrO₂ layer allows achieving ahigh dielectric constant in a range of approximately 40 due to thecrystallized thin ZrO₂ layer and reducing the leakage current due to theamorphous thin Al₂O₃ layer. The high dielectric constant can contributeto improvement in large capacitance of the capacitor.

FIG. 11 illustrates a simplified diagram of a capacitor structure inaccordance with an eighth specific embodiment of the present invention.A dielectric structure including repeatedly formed triple structures isformed over a lower electrode. Each triple structure includes anamorphous thin Al₂O₃ layer, a crystallized thin ZrO₂ layer, and anotheramorphous thin Al₂O₃ layer laminated in this sequence. The triplestructures are repeatedly formed for a certain number of times N, whereN may range from approximately 2 to 10. The amorphous Al₂O₃ layer isformed to a thickness of approximately 2 Å to 20 Å, while thecrystallized ZrO₂ layer is formed to a thickness of approximately 40 Åto 150 Å. This triple structure including the amorphous Al₂O₃ layer, thecrystallized ZrO₂ layer, the other amorphous Al₂O₃ layer allowsachieving a high dielectric constant in a range of approximately 40 dueto the crystallized thin ZrO₂ layer and reducing the leakage current dueto the amorphous thin Al₂O₃ layer. The high dielectric constant cancontribute to improvement in large capacitance of the capacitor. Thedielectric structures described in FIGS. 4 to 11 are formed using an ALDmethod.

FIG. 12 illustrates a diagram to illustrate an ALD method for forming adielectric structure in accordance with the first to eighth specificembodiments of the present invention. The diagram illustrates a seriesof mechanism for depositing a dielectric structure using the ALD method.

A typical ALD method includes performing four steps. A first step (A)includes loading a wafer in a chamber and supplying a source gas intothe chamber. A second step (B) includes supplying a purge gas into thechamber. A third step (C) includes supplying a reaction gas into thechamber. A fourth step (D) includes supplying a purge gas into thechamber.

The first step (A) includes supplying a source gas into a targetchamber. In detail, a wafer is loaded in a deposition chamber, and thesource gas including a zirconium (Zr) source material or aluminum (Al)source material is supplied into the chamber. Thus, the source gas isadsorbed on the wafer.

The source gas is chemically adsorbed on the wafer, and consequently, asource gas layer is formed over the wafer. The Zr source may utilize aprecursor including one selected from a group consisting of Zr(O-tBu)₄,Zr[N(CH₃)₂]₄, Zr[N(C₂H₅)CH₃]₄, Zr[N(C₂H₅)₂]₄, Zr(TMHD)₄,Zr(OiC₃H₇)₃(TMHD), and a combination thereof.

The second step (B) includes supplying a purge gas into a targetchamber. In detail, the purge gas is supplied into the target chamber toremove parts of the source gas loosely bonded to the source gas layerformed over the wafer or non-reacted parts of the source gas. Thus, onlythe source gas layer having a uniform surface is formed over the wafer.The purge gas is an inert gas, and may include one selected from a groupconsisting of argon (Ar), helium (He), nitrogen (N₂) and a combinationthereof.

The third step (C) includes supplying a reaction gas into the chamber.The reaction gas may include one selected from a group consisting ofozone (O₃), oxygen (O₂) plasma, and water (H₂O).

The reaction gas is supplied into the chamber and induces a reactionbetween the source gas layer and the reaction gas to form a zirconiumdioxide (ZrO₂) layer. Thus, a material layer at an atomic layer level isformed over the wafer. That is, the ZrO₂ layer is formed over the waferthrough the reaction between the source gas layer and the reaction gas.

The fourth step (D) includes supplying a purge gas into the chamber. Thepurge gas is supplied into the chamber to remove non-reacted parts ofthe reaction gas and reaction by-products. Consequently, the ZrO₂ layeris formed evenly over the wafer. The purge gas is an inert gas, and mayinclude one selected from a group consisting of Ar, He, N₂ and acombination thereof.

Accordingly, an atomic layer having a desired thickness is obtained byrepeatedly performing a unit cycle including supplying the source gas(the first step), supplying the purge gas (the second step), supplyingthe reaction gas (the third step), and supplying the purge gas (thefourth step).

Meanwhile, the ALD method uses one of a single-wafer type apparatus anda batch type furnace. A temperature ranging from approximately 200° C.to approximately 350° C. is maintained in the chamber when thesingle-wafer type apparatus is used.

An aluminum oxide (Al₂O₃) layer is formed over the ZrO₂ layer using anALD method. FIG. 12 is also used to describe this process since theembodying fundamentals are substantially the same.

A first step (A) includes loading a wafer in a chamber and supplying asource gas into the chamber. A second step (B) includes supplying apurge gas into the chamber. A third step (C) includes supplying areaction gas into the chamber. A fourth step (D) includes supplying apurge gas into the chamber.

The first step (A) includes supplying a source gas into a targetchamber. A wafer is loaded in a deposition chamber, and the source gasincluding an aluminum (Al) source material is supplied into the chamber.Thus, the source gas is adsorbed on the wafer.

The source gas is chemically adsorbed on the wafer, and consequently, asource gas layer is formed over the wafer. The Al source may utilize aprecursor including Al(CH₃)₃.

The second step (B) includes supplying a purge gas into the chamber. Thepurge gas is supplied into the chamber to remove parts of the source gasloosely bonded to the source gas layer formed over the wafer ornon-reacted parts of the source gas. Thus, only the source gas layerhaving a uniform surface is formed over the wafer. The purge gas is aninert gas, and may include one selected from a group consisting of Ar,He, N₂, and a combination thereof.

The third step (C) includes supplying a reaction gas into the chamber.The reaction gas may include one selected from a group consisting ofozone (O₃), oxygen (O₂) plasma, and water (H₂O).

The reaction gas is supplied into the chamber and induces a reactionbetween the source gas layer and the reaction gas to form an Al₂O₃layer. Thus, a material layer at an atomic layer level is formed overthe wafer. That is, the Al₂O₃ layer is formed over the wafer through thereaction between the source gas layer and the reaction gas.

The fourth step (D) includes supplying a purge gas into the chamber. Thepurge gas is supplied into the chamber to remove non-reacted oxygensource and reaction by-products. Consequently, the Al₂O₃ layer is formedevenly over the wafer. The purge gas is an inert gas, and may includeone selected from a group consisting of Ar, He, N₂, and a combinationthereof.

Accordingly, an atomic layer having a desired thickness is obtained byrepeatedly performing a unit cycle including supplying the source gas(the first step), supplying the purge gas (the second step), supplyingthe reaction gas (the third step), and supplying the purge gas (thefourth step). At this time, a substrate temperature is maintained torange from approximately 100° C. to approximately 500° C.

A thermal treatment is performed to form a crystallized ZrO₂ layer or toincrease the crystallization of the ZrO₂ layer. The thermal treatment onthe thin layer is performed at a temperature ranging from approximately500° C. to approximately 800° C. in an atmosphere of N₂ or Ar with acontrolled oxygen quantity or in a vacuum.

The thermal treatment is performed using one of a furnace thermaltreatment and a rapid thermal treatment. Meanwhile, the ALD methodutilizes one of a single-wafer type apparatus and a batch type furnace.

FIG. 13 illustrates a simplified diagram of a capacitor structure inaccordance with a ninth specific embodiment of the present invention. Adual structure of a crystallized thin ZrO₂ layer and an amorphous thinZrAlO_(x) layer laminated in this sequence order is formed as adielectric structure over a lower electrode. The crystallized ZrO₂ layeris formed to a thickness of approximately 40 Å to 150 Å, while theamorphous ZrAlO_(x) layer is formed to a thickness of approximately 2 Åto 20 Å. This dual structure of the crystallized ZrO₂ layer and theamorphous ZrAlO_(x) layer allows achieving a high dielectric constant ina range of approximately 40 due to the crystallized thin ZrO₂ layer andreducing the leakage current due to the amorphous thin ZrAlO_(x) layer.The high dielectric constant can contribute to improvement in largecapacitance of the capacitor.

FIG. 14 illustrates a simplified diagram of a capacitor structure inaccordance with a tenth specific embodiment of the present invention. Adual structure of an amorphous thin ZrAlO_(x) layer and a crystallizedthin ZrO₂ layer laminated in this sequence order is formed as adielectric structure over a lower electrode. The amorphous ZrAlO_(x)layer is formed to a thickness of approximately 2 Å to 20 Å, while thecrystallized ZrO₂ layer is formed to a thickness of approximately 40 Åto 150 Å. This dual structure of the amorphous ZrAlO_(x) layer and thecrystallized ZrO₂ layer allows achieving a high dielectric constant in arange of approximately 40 due to the crystallized thin ZrO₂ layer andreducing the leakage current due to the amorphous thin ZrAlO_(x) layer.The high dielectric constant can contribute to improvement in largecapacitance of the capacitor. The crystallized ZrO₂ layer and theamorphous ZrAlO_(x) layer illustrated in FIGS. 13 and 14 are formed byemploying an ALD method.

FIG. 15 illustrates a diagram to illustrate an ALD method in accordancewith the ninth and tenth specific embodiments of the present invention.The diagram illustrates a series of mechanism for depositing adielectric structure using the ALD method.

A typical ALD method includes performing four steps. A first step (A)includes loading a wafer in a chamber and supplying a source gas intothe chamber. A second step (B) includes supplying a purge gas into thechamber. A third step (C) includes supplying a reaction gas into thechamber. A fourth step (D) includes supplying a purge gas into thechamber.

The first step (A) includes supplying a source gas into a targetchamber. In detail, a wafer is loaded in a deposition chamber, and thesource gas including Zr source or Al source is supplied into thechamber. Thus, the source gas is adsorbed on the wafer.

The source gas is chemically adsorbed on the wafer, and consequently, asource gas layer is formed over the wafer. The Zr source may utilize aprecursor including one selected from a group consisting of Zr(O-tBu)₄,Zr[N(CH₃)₂]₄, Zr[N(C₂H₅)CH₃]₄, Zr[N(C₂H₅)₂]₄, Zr(TMHD)₄,Zr(OiC₃H₇)₃(TMHD), and a combination thereof. The Al source may utilizea precursor including Al(CH₃)₃.

The second step (B) includes supplying a purge gas into the chamber. Thepurge gas is supplied into the chamber to remove parts of the source gasloosely bonded to the source gas layer formed over the wafer ornon-reacted parts of the source gas. Thus, only the source gas layerhaving a uniform surface is formed over the wafer. The purge gas is aninert gas, and may include one selected from a group consisting of Ar,He, N₂, and a combination thereof.

The third step (C) includes supplying a reaction gas into the chamber.The reaction gas may include one selected from a group consisting of O₃,O₂ plasma, and H₂O.

The reaction gas is supplied into the chamber and induces a reactionbetween the source gas layer and the reaction gas to form a ZrAlO_(x)layer, where ‘x’ representing an atomic ratio of oxygen is a certainpositive number. Thus, a material layer at an atomic layer level isformed over the wafer. That is, the ZrAlO layer is formed over the waferthrough the reaction between the source gas layer and the reaction gas.

The fourth step (D) includes supplying a purge gas into the chamber. Thepurge gas is supplied into the chamber to remove non-reacted parts ofoxygen gas and reaction by-products. Consequently, the ZrAlO_(x) layeris formed evenly over the wafer. The purge gas is an inert gas, and mayinclude one selected from a group consisting of Ar, He, N₂, and acombination thereof.

Accordingly, an atomic layer having a desired thickness is obtained byrepeatedly performing a unit cycle including supplying the source gas(the first step), supplying the purge gas (the second step), supplyingthe reaction gas (the third step), and supplying the purge gas (thefourth step).

A thermal treatment is performed to form a crystallized ZrO₂ layer or toincrease the crystallization of the ZrO₂ layer. The thermal treatment isperformed at a temperature ranging from approximately 500° C. toapproximately 800° C. after a dielectric structure is formed.

The thermal treatment is performed using one of a furnace thermaltreatment and a rapid thermal treatment. Meanwhile, the ALD methodutilizes one of a single-wafer type apparatus and a batch type furnace.

In accordance with the specific embodiments, forming a capacitor usingthe dielectric structure including the crystallized ZrO₂ layer and theamorphous Al₂O₃ layer may allow increasing the dielectric constant ofthe capacitor while decreasing the leakage current. Thus,characteristics of the capacitor may be improved. Although the ZrO₂layer is used as the crystallized material in the specific embodimentsof the present invention, a crystallized hafnium dioxide (HfO₂) layer ora crystallized lanthanum trioxide (La₂O₃) layer may be used as thecrystallized material.

In accordance with the specific embodiments, the characteristics of thecapacitor may be improved by maintaining the crystallization of the ZrO₂layer, which is a high-k dielectric layer, and increasing the dielectricconstant by employing the amorphous Al₂O₃ layer as a part of thelaminate structure, while decreasing the leakage current characteristic.

While the present invention has been described with respect to thespecific embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

1. A capacitor comprising: a lower electrode; a dielectric structureformed over the lower electrode, the dielectric structure including atleast one crystallized zirconium oxide (ZrO₂) layer having a firstthickness and at least one amorphous zirconium aluminum oxide(ZrAlO_(x)) layer having a second thickness, where ‘x’ represents anatomic ratio of oxygen and is a positive number; and an upper electrode,wherein the first thickness is different from the second thickness, andthe first thickness is greater than the second thickness.
 2. Thecapacitor of claim 1, wherein the dielectric structure is formed in adual structure by sequentially laminating the crystallized ZrO₂ layerand the amorphous ZrAlO_(x) layer over the lower electrode.
 3. Thecapacitor of claim 1, wherein the dielectric structure is formed in adual structure by sequentially laminating the amorphous ZrAlO_(x) layerand the crystallized ZrO₂ layer over the lower electrode.
 4. Thecapacitor of claim 1, wherein the first thickness is approximately 40 Åto 150 Å.
 5. The capacitor of claim 1, wherein the second thickness isapproximately 2 Å to 20 Å.
 6. The capacitor of claim 1, wherein thecrystallized ZrO₂ layer and the amorphous ZrAlO_(x) layer are formedthrough performing an atomic layer deposition (ALD) method.
 7. A methodfor fabricating a capacitor, the method comprising: forming a lowerelectrode over a certain structure; forming a dielectric structure overthe lower electrode including at least one crystallized zirconium oxide(ZrO₂) layer having a first thickness and at least one amorphouszirconium aluminum oxide (ZrAlO_(x)) layer having a second thickness,where ‘x’ represents an atomic ratio of oxygen and is a positive number;and forming an upper electrode over the dielectric structure, whereinthe first thickness is different from the second thickness, and thefirst thickness is greater than the second thickness.
 8. The method ofclaim 7, wherein forming the dielectric structure comprises sequentiallylaminating the crystallized ZrO₂ layer and the amorphous ZrAlO_(x) layerover the lower electrode.
 9. The method of claim 7, wherein forming thedielectric structure comprises sequentially laminating the amorphousZrAlO_(x) layer and the crystallized ZrO₂ layer over the lowerelectrode.
 10. The method of claim 7, wherein the first thickness isapproximately 40 Å to 150 Å.
 11. The method of claim 7, wherein thesecond thickness is approximately 2 Å to 20 Å.
 12. The method of claim7, wherein forming the dielectric structure including the crystallizedZrO₂ layer and the amorphous ZrAlO_(x) layer comprise performing anatomic layer deposition (ALD) method.